Three-part muffler with side branch chambers



June 6, 1967 c. J. HANCHETT 3,323,613

THREE-PART MUFFLER WITH SIDE BRANCH CHAMBERS Filed Oct. 26, 1964 R 1 M m m1 a m W 4 H I (awry United States Patent 3,323,613 THREE-PART MUFFLER WITH SIDE BRANCH CHAMBERS Clifford J. Hanchett, Grass Lake, Mich., assignor to Walker Manufacturing Company, a corporation of Delaware Filed Oct. 26, 1964, Ser. No. 406,386 4 Claims. (Cl. 18148) This invention relates generally to mufllers, especially those of the type used in exhaust systems for internal combustion engines.

It is an object of the present invention to provide a straight through flow mufiler that is of the same length and volume as similar type prior mufiiers but which is more effective in attenuating sound than such prior mufilers.

It is still another object of the present invention to provide a straight through flow mufller which combines a spit chamber and a tuning chamber in an extremely compact unit.

It is yet another object of the present invention to provide an improved exhaust mufller of a simple design that can be easily assembled and economically manufactured.

The invention achieves the foregoing and other objects by means of a mufiler in which a center tube provides an unobstructed, straight through flow path for gas. The center tube is contained within an outer tube or housing and its inlet is spaced downstream a slight distance from the inlet to the housing. An intermediate shell surrounds the center tube and defines an annular tuning passage that is open at both ends to afford direct communication between the gas entering the rnuffier through the housing inlet and a tuning volume between the housing and center tube. The incoming gas therefore directly drives or pressurizes the tuner to give greater impedance and dwell time and provide improved attenuation as compared with Helmholtz resonators constructed by prior methods.

Other objects and advantages of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

FIGURE 1 is a longitudinal cross-sectional view of a preferred embodiment of the exhaust muffler of the present invention;

FIG. 2 is a transverse cross-sectional view taken along the line 2-2 of FIG. 1;

FIG. 3 is a transverse cross-sectional view taken along the line 3-3 of FIG. 1;

FIG. 4 is a transverse cross-sectional view taken on the line 44- of FIG. 1; and

FIG. 5 is a transverse cross-sectional view taken along the line 55 of FIG. 1.

Referring now to FIG. 1 of the drawings, an exhaust muflier comprises a tubular outer shell or housing 12 which is necked-down or swaged radially inwardly at its opposite ends into inlet and outlet bushings 14 and 16, respectively. An elongated cylindrical center tube 18, which preferably has an outside diameter equal to the inside diameter of the bushings 14 and 16, extends coaxially Within the housing 12 and defines a central gas-flow passage therethrough. The right end of the gas flow tube 18 is supported within the outer tube 12 by being spotwelded, as seen at x, to the inner periphery of the outlet bushing 16. As illustrated in FIGS. 1 and 4, the tube 18 is also supported in a gas tight joint by the inner periphery of a reduced diameter annulus provided by four circum ferentially spaced pinched-down sections, generally designated 20, that are formed in a medial section of the muffler housing 12 by pinched portions 19.

A hollow cylindrical tuning tube 22, which is some- 3,323,613 Patented June 6, 1967 what larger in diameter than the tube 18 but which is smaller in diameter than the outer tube 12, extends concentrically around the inlet end of the tube 18. As seen in FIGS. 1 and 2, the opposite ends of the tuning tube 22 are rigidly secured to the shell 18 in gas flow joints by two pairs of diametrically opposed pressed in portions 24 that are formed one pair at each end of the tube 22 and are spotwelded to the outer periphery of the shell 18. The shell portions 25 between the sections 24 are spaced from the tube 18 to provide openings at each end of the annular space between the shell and tube.

The inlet ends of the tube 18 and the tuning tube 22 are supported within the housing 12 between four circumferentially spaced pinched-down sections, generally designated 26, which are identical in construction to the aforementioned pinched-down sections 20, and which are spotwelded in a gas tight joint to the outer periphery of the tuning tube 22, as seen in FIG. 3.

It will be seen that the pinched-down sections 20 and 26 (FIGS. 4 and 3) act as partition means and provide gas tight partitions between the inner periphery of the housing 12 and the outer peripheries of the tube 18 and of the tuning tube 22, respectively. Accordingly, the outer periphery of the rig-ht end of the tube 18, together with the inner periphery of the right end of the housing 12, the pinched-down sections 20 and the outlet bushing 16, define a first closed annular chamber 28 which surrounds the right end of the tube 18. A bank of fine flat louvers, generally designated 30, are formed in tube 18 in the chamber 28 and so that this chamber serves as a spit chamber to attentuate high frequency noise in exhaust gas flowing through tube 187 As seen in FIGURE 1, a small drain hole 29 may be provided on the lowermost side of the housing 12 to permit condensate to drain from the interior of the spit chamber 28.

The space between the pinch-down joints 20 and 26 comprises a tuning chamber 32 and the space between joint 26 and the inlet end of the outer tube 12 comprises an inlet chamber 33. The two chambers 32 and 33 are connected by the annular tuning passage 34 that is formed by shell 22 around the center tube 18.

If desired, the ends of the outer tube 12 may be swaged down from the larger diameter to form the bushings 14 and 16. Manufacturing may be facilitated by pinching the bushing 16 to tightly lit the outside of tube 18 as I indicated by pinches 36. The reduced diameter end of the tube 18 may be extended and bent as indicated to form a tailpipe and tailspout portion 387 In operation as an exhaust gas muffler for internal combustion engines, the bushing 14 is connected to receive the exhaust gas from the exhaust manifold. Gas entering the muffler passes into inlet chamber 33 and can flow in a straight-through unobstructed path through tube 18 to the outlet. Since tuning passage 34 is in direct, in-line communication with the gas entering inlet chamber 33, the tuning chamber 32 will be pressurized or driven by the incoming gas and will operate at a higher mean pressure than the Helmholtz resonators conventionally used in exhaust mufilers. Consequently, its impedance and elfectiveness are increased. The arrangement also minimizes the required length of shell 22 to provide the desired throat length. Since the cross-sectional area of passage 34 and its end openings provided by sections 25 is substantially less than that of volume 32 outflow is restricted and the dwell time of pressure pulses enhanced.

The resonator provided by the tuning passage 34 and the chamber 32 is tuned by known methods (control of throat area and length and chamber volume) to attenuate a desired note of frequency. Higher frequencies, roughness, scratchiness, and spit are attenuated by the spit chamber 28 as the gas flows through the tube 18.

It is noted that many functions and advantages are provided by the disclosed mufiler which consists of only three parts.

Modifications may be made in the structure illustrated without departing from the spirit and scope of the invention.

I claim:

1. In a muffler, an exhaust gas tubular housing, means on the opposite ends of said housing communicating exhaust gases to and from said housing and including an inlet chamber, a center tube extending coaxially of said housing and defining a central gas flow path therethrough and receiving gas from said inlet chamber, said housing and said tube defining an elongated annular chamber therebetween, said housing being reduced in diameter and in engagement with the outer periphery of said tube thereby dividing said annular chamber into a tuning chamber and a spit chamber, a tuning tube around said center tube extending within said tuning chamber coaxially of said housing, said tuning tube being open at both ends with one end opening into said inlet chamber and the other into said tuning chamber, one end of said tuning tube being of reduced diameter and in engagement with the outer periphery of said center tube and the opposite end of said tuning tube being secured to said housing.

2. In a mufller having an inlet end, an inner gas flow tube, a muffler housing defining a tuning chamber around said gas flow tube, a tuning tube open at both ends and extending around said gas flow tube within said chamber, said tuning tube being secured at one end to said gas flow tube and at the opposite end to said housing, said tuning tube and gas flow tube being spaced downstream from said inlet end and the space between them and said inlet end comprising an inlet chamber receiving gas from said inlet and furnishing it to both said tubes.

3. An exhaust gas mufiier for silencing a predetermined note and higher frequencies including roughness and spit noise comprising a housing having an inlet end and an outlet end, means in the housing forming an inlet chamber into which all gas flows from said inlet end, a gas flow tube supported in said housing having an inlet end opening into said inlet chamber and all gas from said inlet end flowing into said inlet chamber and through said gas fiow tube to reach said inlet end, means in the housing forming a tuning chamber, a tuning plate tube open at both ends positioned around said gas flow tube and opening at its downstream end into said tuning chamber and forming the sole opening into and out of said tuning chamber, the inlet end of said tuning tube opening into said inlet chamber and arranged in parallel with the inlet end of said gas flow tube so that gas flowing through said inlet chamber flows directly into the tuning tube and pressurizes the tuning chamber, said tuning tube and tuning chamber being tuned to attenuate said predetermined note, and means in the housing forming a spit chamber around the gas flow tube downstream of the tuning chamber and said gas flow tube having perforations therein connecting its inside with said spit chamber so that said spit chamber attenuates higher frequencies, roughness, and spit.

4. In an exhaust gas muffier, a tubular housing, means on the opposite ends of said housing communicating exhaust gases to and from said housing and including an inlet chamber, a center tube extending coaxial ly of said housing and defining a central gas flow path therethrough and receiving gas from said inlet chamber, said housing and said tube defining an elongated annular chamber therebetween, a first portion of said housing being reduced in diameter and in engagement with the outer periphery of said tube thereby dividing said annular chamber into a tuning chamber and a spit chamber, a tuning tube around said center tube extending within said tuning chamber coaxially of said housing, said tuning tube being open at both ends with one end opening into said inlet chamber and the other into said tuning chamber, a second portion of said housing being reduced in diameter to engage said tuning tube and act with said first portion to define said tuning chamber and with the inlet end of the housing to define said inlet chamber, said housing, center tube, and tuning tube comprising the only parts of said muffler and said muffler therefore consisting of only three parts.

References Cited UNITED STATES PATENTS 2,112,964 4/1938 MacKenzie 181-48 2,367,753 1/1945 Buck. 2,514,998 7/1950 Fundom 181-61 X 2,660,25 6 11/ 1953 Walker. 3,104,733 9/1963 Ludlow 181-36 3,209,861 10/1965 Whitney 18159 3,233,698 2/ 1966 Powers.

FOREIGN PATENTS 1,189,372 3/1959 France.

484,771 5/193 8 Great Britain.

892,780 3/ 1962 Great Britain.

RICHARD B. WILKINSON, Primary Examiner.

STEPHEN J. TOMSKY, Examiner.

R. S. WARD, Assistant Examiner. 

1. IN A MUFFLER, AN EXHAUST GAS TUBULAR HOUSING, MEANS ON THE OPPOSITE ENDS OF SAID HOUSING COMMUNICATING EXHAUST GASES TO AND FROM SAID HOUSING AND INCLUDING AN INLET CHAMBER, A CENTER TUBE EXTENDING COAXIALLY OF SAID HOUSING AND DEFINING A CENTRAL GAS FLOW PATH THERETHROUGH AND RECEIVING GAS FROM SAID INLET CHAMBER, SAID HOUSING AND SAID TUBE DEFINING AN ELONGATED ANNULAR CHAMBER THEREBETWEEN, SAID HOUSING BEING REDUCED IN DIAMETER AND IN ENGAGEMENT WITH THE OUTER PERIPHERY OF SAID TUBE THEREBY DIVIDING SAID ANNULAR CHAMBER INTO A TUNING CHAMBER AND A SPIT CHAMBER, A TUNING TUBE AROUND SAID CENTER TUBE EXTENDING WITHIN SAID TUNING CHAMBER COAXIALLY OF SAID HOUSING, SAID TUNING TUBE BEING OPEN AT BOTH ENDS WITH ONE END OPENING INTO SAID INLET CHAMBER AND THE OTHER INTO SAID TUNING CHAMBER, ONE END OF SAID TUNING TUBE BEING OF REDUCED DIAMETER AND IN ENGAGEMENT WITH THE OUTER PERIPHERY OF SAID CENTER TUBE AND THE OPPOSITE END OF SAID TUNING TUBE BEING SECURED TO SAID HOUSING. 